Between 1990 and 1995, ISUZU (ISZ) automobiles RV lines, specifically Trooper with MUA Type Transfer (Fig.1), had problems with loud locomotive noise, also known as whine noise. In July 1992, HINDUSTAN MOTORS (HM) found the same problem with its 4X2 MSG Type Transmission (Fig.2).† At first, we looked to the gear precision and tooth contact pattern on both good and defective transfer units for the cause of the whine noise; unfortunately, after investigation, nothing was found. In total, we checked the involute helicoid, outer shape of shaft and all faces of gear and root of gear. Consequently, we found the whine noise was caused by the root running out of gear resulting in an imbalance in the face and the shape of shaft, causing each to run out. At the same time, we found that minimized the unbalance value will solve the whine noise issue. We used two test units (good and defective) to conduct the research and to resolve the whine noise problem.